1. Field of the Invention
This invention relates generally to access devices, such as trocars, and more specifically to access devices including at least one septum valve.
2. Discussion of the Prior Art
Laparoscopic surgery is conducted through trocars which extend across the abdominal wall and provide channels through which instruments such as scopes, retractors and staplers can be inserted to perform surgery in the abdominal cavity. As a part of this procedure, the abdomen is inflated with an insufflation gas to maintain the abdomen in a distended state. Valves are typically provided in the trocars to form seals around the instruments in order to prevent leakage of this insufflation gas. A variable as it is able to conform to any size of instrument, regardless of its diameter, without increasing the friction or drag on the instrument. A variable diameter septum valve of this nature is disclosed and claimed by applicant in the parent application Ser. No. 07/732,141, filed on Jul. 18, 1992 and entitled Lever Actuated Septum Seal.
Variable diameter seals have a high degree of compliance which is of particular advantage in accommodating different sizes of instruments. However, this compliance can present a problem if a particular instrument is bifurcated or is inserted off center. Under these circumstances, the sharp point of the instrument can localize forces along the side of the valve providing undesirable cupping and perhaps tearing of the seal. This can occur with any septum seal, although the highly compliant variable diameter seals appear to be most susceptible to damage.
The off-axis insertion of an instrument can also be a problem once the instrument extends through the orifice of the septum valve. If this orifice is pulled off-axis, it tends to develop a "cat-eye" which degrades the seal around the instrument and permits for undesirable leakage.